The invention relates to the production of cheese, especially cream cheese and cottage cheese. More specifically, the invention relates to methods for increasing dairy protein incorporation into curd during cheese production using transglutaminase. This invention also relates to methods for reducing syneresis in cheese products, especially cream cheese and cottage cheese, using transglutaminase.
Cheese compositions are generally prepared from dairy liquids by processes that include treating the liquid with a coagulating or clotting agent. The coagulating agent may be a curding enzyme, an acid, or a suitable bacterial culture. The coagulum or curd that results generally incorporates transformed casein, fats including natural butter fat, and flavorings (especially those arising when bacterial cultures are used). The curd is usually separated from the whey. The resulting liquid whey generally contains soluble proteins not affected by the coagulation; such proteins are, of course, not incorporated into the coagulum. The inability of whey proteins to be retained in the coagulum is an important factor contributing to a lack of efficiency in production of cheese curds, and to a reduction in overall yield relating to the incorporation of protein solids present in the starting dairy liquids into resulting cheese curds. Therefore, there remains a need for effective methods of improving the efficiency of protein incorporation into curd during cheese production.
Soft cheeses such as cream cheese and cottage cheese products usually suffer water separation during storage due to the process of syneresis. The resulting acid whey (i.e., separated water phase), although it contains substantial amounts of dairy proteins, cannot be efficiently utilized. Moreover, consumers generally find such water separation objectionable. Therefore, there remains a need for improved methods for producing soft cheeses wherein syneresis is reduced.
Transglutaminases are enzymes which catalyze the crosslinking of proteins. These enzymes have a broad occurrence in nature and may be obtained, for example, from microorganisms such as those belonging to the genus Streptoverticillium or from Bacillus subtilis, from various Actinomycetes and Myxomycetes, from fish and other marine sources, from plant sources, and from animal sources (especially mammals). Food processing methods employing transglutaminases have been disclosed in recent years. For example, Japanese Patent 59059151 discloses treating an emulsion containing proteins, oils or fats, and water with transglutaminase to produce a gelatinous, crosslinked gel. Japanese Patent 02276541 discloses a heat-resistant food protein having a fibrous texture. The fibrous texture is developed by treatment of a protein hydrogel with a transglutaminase in the presence of calcium ions to induce crosslinking of the surface of a fiber bundle.
U.S. Pat. No. 5,156,956 discloses a transglutaminase purified from strains of the genus Streptoverticillium, and the use of this enzyme to produce gel type foods. This transglutaminase catalyzes formation of protein gelation products from protein solutions to produce conventional gel foodstuffs such as yoghurt, jelly, cheese, gel cosmetics, and the like.
U.S. Pat. No. 5,731,183 discloses a transglutaminase purified from strains of Bacillus subtilis, having particular physical and enzymatic characteristics, and a method for producing protein, peptide, or non-protein amino acid polymers that are crosslinked via their glutamine and lysine residues to form intermolecular or intramolecular conjugates. The crosslinked protein polymers produced using transglutaminase are reported to be useful in a variety of food substances.
Methods have been proposed for increasing the recovery of whey protein into cheese products using transglutaminase. For example, U.S. Pat. No. 6,093,424 relates to treatment of a dairy liquid such as milk with transglutaminase and a non-rennet protease to generate cheese curd for hard, soft, or semi-soft cheeses.
U.S. Pat. No. 5,681,598 and its European counterpart EP 0 711 504 A1 disclose a process for producing cheese using transglutaminase added at the same time as both a clotting enzyme and a lactic-acid producing culture, and the milk is then incubated.
Patent publication WO 97/01961 discloses a method for producing cheese using transglutaminase. Transglutaminase is added to milk, followed by a short incubation period, after which a clotting enzyme or curding agent is added to the milk to produce curd.
The current invention provides processes for producing cheeses that improve the efficiency of dairy protein incorporation into cheese curd during production. Additionally, the cheeses produced using the process have improved qualities, including decreased syneresis.
The current invention provides processes for cheese manufacturing that significantly increase the yield of cheese produced by using the enzyme transglutaminase and an acidifying step to crosslink dairy proteins during cheese manufacturing. The cheese products are less fragile and have reduced syneresis. Additionally, the cheese products have greater viscosity and firm texture.
In one aspect, the current invention provides a process for making a cheese product comprising:
(i) providing a dairy liquid comprising dairy proteins;
(ii) crosslinking and curding the dairy liquid by adding an acidifying agent and adding a transglutaminase to the dairy liquid for a crosslinking and curding time, and under crosslinking and curding conditions, sufficient to crosslink at least a portion of the dairy proteins and to form a curd and a liquid whey;
(iii) disrupting and heating the curd;
(iv) separating the curd from the liquid whey; and
(v) collecting the curd.
Typically, a coagulating enzyme is not added during step (ii). In certain embodiments, a coagulating enzyme is not added during any step of the process. The dairy liquid may be pasteurized.
In certain embodiments, transglutaminase is used in step (ii) at concentrations of less than 10 units per gram dairy liquid, preferably less than 5 units per gram, more preferably less than 1 unit per gram. In certain embodiments, transglutaminase is used at a concentration of about 0.4 to about 0.8 units per gram dairy liquid.
In one embodiment, the addition of the acidifying agent during step (ii) is performed before the addition of transglutaminase. In a further embodiment, the process further comprises heating the crosslinked dairy liquid at a temperature and for a time sufficient to inactivate the transglutaminase after step (ii) and before step (iii).
In certain embodiments, the acidifying agent is a culture containing a lactic acid-producing microbe. In one embodiment using a lactic acid-producing microbe, the resulting pH of the dairy liquid is about 4.2 to about 5.2, preferably about 4.4 to about 4.8, and most preferably about 4.5 to about 4.7.
In certain embodiments, the acidifying agent is a food grade acid. In one embodiment, the food grade acid is selected from the group consisting of citric acid, lactic acid, glucono delta lactone, phosphoric acid, acetic acid or vinegar, and the like.
In certain embodiments, the dairy liquid comprises dairy ingredients selected from milk, reconstituted dry milk, concentrated milk, milk protein concentrate, whey, reconstituted whey, whey protein concentrate, and cream.
In certain embodiments, the dairy liquid comprises cream and a dairy ingredient selected from the group consisting of milk, reconstituted dry milk, concentrated milk, milk protein concentrate, whey, reconstituted whey, and whey protein concentrate. For these embodiments, the cheese is typically cream cheese. In one embodiment where the cheese is cream cheese, the cooking in step (iv) is performed by heating the curd and whey to about 80xc2x0 C. for about 30 minutes.
In certain embodiments, the dairy liquid is skim milk, concentrated skim milk, reconstituted nonfat dry milk, whey protein, or milk protein concentrate. Typically, where the dairy liquid is skim milk, the resulting cheese is cottage cheese. In one embodiment where the dairy liquid is skim milk, the cooking in step (iv) is performed by increasing the temperature of the curd and whey from about 30 to about 60xc2x0 C. over a period of about 15 to about 150 minutes, and more preferably over a period of about 60 minutes. Typically, where the resulting cheese is cottage cheese, the crosslinking and curding time is from about 1 hour to about 14 hours and the crosslinking and curding conditions include a temperature of about 15 to about 55xc2x0 C., preferably from about 3 hours to about 6 hours at a temperature of about 30 to about 34xc2x0 C., more preferably at about 32xc2x0 C.
Typically, where the resulting cheese is cream cheese, the crosslinking and curding time is from about 1 hour to about 24 hours and the crosslinking and curding conditions include temperatures of about 18 to about 50xc2x0 C., preferably from about 15 hours to about 19 hours at a temperature of about 22 to about 28xc2x0 C. In one embodiment, the crosslinking and curding is carried out for about 17 hours at a temperature of about 25xc2x0 C.
In significant embodiments of the process of the present invention, the transglutaminase is isolated from a bacterial source, a fungus, a mold, a fish, or a mammal. In one preferred embodiment, the transglutaminase is isolated from a bacterial source, preferably from the genus Streptoverticillium. Mixtures of transglutaminase from different sources can be used.
The processes of the current invention for making cream cheese products may include an additional homogenization step after the curd is collected. The homogenization may be carried out at pressures of up to about 10000 psi, preferably up to about 3500 psi, and most preferably up to about 5000 psi.
In another aspect, the current invention is a cheese product produced by a process as described above, including any of the embodiments described above.